Bug ID 1970969: Stale Record Answers counter increments for SERVFAIL responses from DNS resolver cache

Last Modified: Jun 28, 2025

Affected Product(s):
BIG-IP TMOS(all modules)

Known Affected Versions:
16.1.5, 16.1.5.1, 16.1.5.2, 16.1.6, 17.1.2.1, 17.1.2.2

Opened: Jun 24, 2025

Severity: 3-Major

Symptoms

Stale Record Answers counter increments incorrectly when no stale record is served and a SERVFAIL is sent.

Impact

Leads to incorrect Stale Record Answers stat, potentially misleading monitoring, troubleshooting, and operational decisions.

Conditions

-- Configure DNS cache resolver with a forwarder. -- Make sure forwarder does not respond to DNS queries. -- Enable 'ltm dns cache global-settings serve-expired' -- Send a few DNS requests to DNS cache for a record which is to be handled by not responding forwarder. -- Observe 'Stale Record Answers' counter for DNS cache.

Workaround

None

Fix Information

None

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips